This invention relates in general to a mechanism for controlling the temperature of a heating appliance such as a kitchen range, and more particularly relates to controlling the temperature of localized “hot spots”.
It is known to make both gas and electric ranges in order to comply with numerous safety codes, specifically those established by Underwriters Laboratory (UL). Several of these codes relate to the external temperatures of side and top panels of the ranges. Since kitchen ranges are typically positioned adjacent other appliances or are built in next to cabinets, the side panels of the range are close to, or are in direct contact with these other items. It would not be advantageous if the temperature were to rise too high. Another feature creating high temperatures in many ranges made today is that the ranges are self-cleaning. A self-cleaning range incorporates several features, including the initial application of high heat at the top of the range cavity to initiate the operation of a catalytic smoke eliminator before heavy soils on the side and bottom walls are volatized. Heat is then supplied for a period of time to maintain at least a minimum required temperature in the range for pyrolysis of the soils. The heat is controlled to prevent the temperature from exceeding the operating or softening temperature of the enamel on the range liner walls while maintaining the temperature of all parts of the range liner walls within the effective self-clean temperature range.
Manufacturers have used a number of different techniques to control the self-cleaning cycle. Typically, however, range controls begin the cycle with full power applied to a broil (upper) heating unit for a fixed amount of time. At some point during the cycle some controls switch to the bake unit as the primary source of heat input, while others use the bake unit to augment the broil unit input. This may be done at full power or at reduced power. Some other manufacturers use a fixed setting cycle switch, such as a bimetal switch for example, to reduce the effective power of the heating units. Other controls use one unit, either the bake or the broil, exclusively for the heat input. In most ranges, however, a thermostat is used to call for heat when needed to satisfy the minimum requirements, and to stop heat input to keep the range liner temperature from exceeding maximum design temperature.
During a self-cleaning cycle, the temperatures within the range can reach up to, or exceed 900° F. During this self-cleaning cycle it is important to control the side and top panel temperature in order to prevent the temperature's being so excessive as to create a fire hazard, or a potential danger should there be human contact with a hot spot. Normally, such temperature controls are achieved by designing the range such that the range cavity is spaced from the side and top panels so as to leave an air gap between the cavity and the panels. Additionally, insulation is typically positioned on or near the side and top panels to further limit the heat transfer to the surfaces of the panels by either conduction or convection.
Although conventional designs have been somewhat effective to control external temperatures of ranges, it would be advantageous to provide a mechanism to control the temperature of the range, particularly in localized areas on the range, to limit or prevent the occurrence of hot spots.